Marshall Studio JTM ST20H 20W Valve Amp Head
The Marshall Studio JTM ST20H is a 20-watt valve amp head that brings back the sound of the JTM45, Marshall's very first amp, at a volume you can live with in a living room or a studio: round cleans through to crunch, with a switch that drops the output to 5 watts.
What sets it apart
- Two 5881 power valves, as on the original JTM45
- 20 W output, cut to 5 W with a single switch
- Two channels you can jump with a short cable
- Switchable series effects loop
- 1/4-inch DI output for the desk
- Made at Marshall's Bletchley factory in England
First-generation tone at a sensible volume
Inspired by the JTM45, the brand's first amp, the Studio JTM follows its circuit with two ECC83s in the preamp, one ECC83 as phase splitter and a pair of 5881s in the power stage. Marshall describes a warm, smooth sound that goes from clean to crunch and starts to break up at far lower volumes than a 50- or 100-watt head.
That is what the 20 W / 5 W switch is for: keeping the power stage working, where the valves add their colour, without waking the whole house.
Two channels, one recipe
The panel follows tradition: a brighter High Treble channel and a rounder Normal channel, each with its own volume (Loudness I and II), then shared bass, middle, treble and presence. There is no master volume and no footswitchable channel. Instead, you link both channels with a short cable between two of the four inputs, then blend the two volumes.
The effects loop and DI output, missing from the original, make life easier with a pedalboard or in the studio.
Specifications
| Type | All-valve amp head |
|---|---|
| Output | 20 W, reducible to 5 W |
| Preamp | 2 × ECC83, plus 1 × ECC83 phase splitter |
| Power valves | 2 × 5881 |
| Channels | 2, jumpable |
| Controls | Normal/Loudness II, High Treble/Loudness I, treble, middle, bass, presence |
| Inputs | 4 × 1/4-inch jacks, high and low sensitivity |
| Speaker outputs | 5 × 1/4-inch jacks (16, 8 or 4 Ω loads) |
| Other outputs | DI on 1/4-inch jack |
| Effects loop | 1, series, switchable |
| Weight | 9.25 kg |
| Dimensions | 500 × 240 × 230 mm |
What it's for
- Sixties blues and rock at home
- Recording valve crunch at low volume
- A round clean platform for overdrive pedals
- Small rooms, with a 1x12 or 2x12 cabinet
Compared with other manufacturers
Other low-wattage valve heads are made by these manufacturers:
| Maker | Model | Output | Power valves |
|---|---|---|---|
| Marshall | Studio JTM ST20H | 20 W or 5 W | 2 × 5881 |
| Orange | OR15 | 15 W or 7 W | 2 × EL84 |
| Friedman | Pink Taco V2 | 20 W | 2 × EL84 |
| Vox | AC15 Custom Head | 15 W | EL84 |
Frequently asked questions
- What is the difference between the Studio JTM and the Studio Vintage?
- The amp each one is based on. The Studio JTM follows the JTM45 and uses 5881 valves; the Studio Vintage follows the 1959 Super Lead and uses EL34s. Size, output and controls are the same.
- How do I jump the two channels?
- Plug the guitar into a high-sensitivity input on one channel, then run a short cable from that channel's low-sensitivity input to an input on the other. The two Loudness knobs then set the blend.
- Is 5 W mode quiet enough for an apartment?
- It lowers the volume a lot, but a valve head is still a real amp: at 5 W it can be loud. Think of it mainly as a way to reach break-up sooner.
Avis clients
Playing the Studio JTM at home? Tell us how you jump the channels.
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